This disclosure relates generally to proximity detection systems at work sites, and in particular to proximity detection systems that allow system response to be altered depending on the particular operational situation.
Proximity detection systems (PDS) and collision avoidance systems (CAS) are now being used throughout much of the industrial world to help prevent pedestrians from being hit by moving vehicles and to prevent vehicles from colliding with each other. Additionally, these systems help keep personnel and vehicles away from dangerous areas or situations, prevent damage to facility elements that can be damaged by mobile machines, and control the actions and movements of vehicles and pedestrians. Telemetrics have expanded the utility of these systems by providing interaction between safety-related elements and by providing objective information about safety events, traffic control, and safety performance of equipment, policies, procedures, and other information. Yet, some industrial applications have not been able to fully utilize these earlier approaches because special circumstances or conditions in some industrial environments prevent the PDS/CAS systems from being effective or practical to use.
Advancement of magnetically-based CAS has made significant safety improvements that help prevent collisions between vehicles, machines, and pedestrians. The high reliability and precision of these low frequency systems has led to a variety of system configurations and devices that protect pedestrians, prevent collisions between vehicles and/or machines, and prevent collisions with facility items. Examples of these devices are disclosed in U.S. Pat. No. 7,420,471 (the '471 patent), U.S. Pat. No. 8,169,335 (the '335 patent), U.S. Pat. No. 8,552,882 (the '882 patent) U.S. Pat. No. 8,232,888 (the '888 patent), U.S. Pat. No. 8,446,277 (the '277 patent), U.S. Pat. No. 8,847,780 (the '780 patent), U.S. Pat. No. 8,710,979 (the '979 patent), U.S. Pat. No. 8,810,390 (the '390 patent) and U.S. patent publication 2014/0191869 (the '869 publication), which patents and publications are herein referred to collectively as the “Frederick patents,” the disclosures of which are incorporated herein by reference in their entireties. The Frederick patents, for example, have been used successfully on, for example, fork trucks, loaders, top picks, floor sweepers, tractors, cranes, and other types of machinery.
However, improvements are needed to allow other additional safety improvements to be made within warehouse settings where storage racks are essential parts of a facility. Materials handling vehicles transport materials into rack areas, store into rack systems, and later retrieve these items. Travels to and from the rack areas usually occur on roadways that connect areas within the facility. Collisions between these vehicles occur while operating within aisles. These collisions result in costly damage and injury to personnel. In addition, pedestrians must occasionally enter such rack areas for a variety of reasons, and can be struck by these materials handling vehicles, in addition to possibly being hit or crushed in other areas within the warehouse. Managing the movement of these machines and the pedestrians has been improved by use of procedures, safety tools, training, detection systems, and other means. However, collisions continue to occur and continue to be a problem.
Previous attempts to help improve the movement of vehicles and personnel by use of electronically-based and/or radio frequency (RF) systems, such as radio-frequency identification (RFID), have usually resulted in an unacceptable number of nuisance alarms. Magnetically-based systems are especially effective for detecting vehicles and pedestrians that are equipped with PDS and CAS since the magnetic fields will pass through racks and other materials to detect where visibility is blocked. However, these magnetic fields may detect other vehicles, even when trucks are safely separated by the storage racks so that they also produce nuisance alarms.
There is a need to maximize the ability to detect vehicles in the aisles between racks while avoiding nuisance alarms from trucks in other aisles, while at the same time also providing detection of pedestrians. A special situation that is especially dangerous is when materials handling systems and/or pedestrians are exiting from an aisle between racks into roadways. A properly configured PDS/CAS that will be effective within rack storage systems can also be able to reliably provide detection and warnings at these intersections.
The current disclosure provides solutions to some of these specific needs by using vector components instead of only using magnetic field strength. Instead of relying solely upon the strength of magnetic fields as a basis for establishing safety boundaries and for providing detection methodologies, the current disclosure makes it possible to utilize unit vectors or vector components of a magnetic field to better differentiate between true safety threats and non-threats that give the appearance of being a threat.